Acute malnutrition is the result of sudden weight loss due to starvation and disease.
How do aid agencies keep track of hunger?
They already know which areas are most at risk and use a wide variety of tools to measure changes in food availability.
These include satellite weather technology to estimate rainfall and crop assessments which can help predict harvests.
They also carry out nutritional surveys so that they know how much people are eating and also examine the political situation which might affect the hunger of a population.
Local staff in the field also channel information from the ground.
Areas of hunger can change dramatically within a single country and these tools create a picture of areas that need special help.